1. Field of the Disclosure
This disclosure relates to an electrode for a fuel cell, a method of forming the fuel cell electrode, a membrane-electrode assembly including the electrode, and a fuel cell system including the electrode.
2. Description of the Related Technology
A fuel cell is a power generation system for producing electrical energy through an electrochemical oxidation-reduction reaction between an oxidant and a fuel such as hydrogen or a hydrocarbon-based material such as methanol, ethanol, natural gas, and the like. The fuel cell is a clean energy source with potential to replace use of fossil fuels. The fuel cell includes a stack composed of unit cells, which together produce various ranges of power output. The fuel cell may have between four and ten times higher energy density than a small lithium battery, and thus, may be used as a small portable power source.
Representative exemplary fuel cells include a direct oxidation fuel cell (“DOFC”) and a polymer electrolyte membrane fuel cell (“PEMFC”). The direct oxidation fuel cell may be a direct methanol fuel cell, which uses methanol as a fuel. The PEMFC has an advantage of high energy density and high power, but also, a drawback of requiring careful handling of hydrogen gas and requiring accessory facilities such as a fuel-reforming processor for reforming methane or methanol, natural gas, and the like, to produce hydrogen gas as a fuel. The DOFC, however, has lower energy density than the PEMFC, but has an advantages that include more easily handling a liquid-type fuel, being operated at a low temperature, and needing no additional fuel reforming processor.
In the aforementioned fuel cell systems, a stack capable of generating electricity includes several to scores of unit cells stacked adjacent to one another. Each unit cell is composed of a membrane-electrode assembly (“MEA”) and a separator (also referred to as a bipolar plate). The MEA is composed of an anode (also referred to as a “fuel electrode” or an “oxidation electrode”) and a cathode (also referred to as an “air electrode” or a “reduction electrode”) separated by a polymer electrolyte membrane.
During operation of the fuel cell systems electricity is generated as follows: A fuel is supplied to the anode and adsorbed on catalysts of the anode and then, oxidized to produce protons and electrons. The electrons are transferred into the cathode via an external circuit, while the protons are transferred into the cathode through the polymer electrolyte membrane. At the same time, an oxidant is supplied to the cathode, which oxidant reacts with the protons and the electrons on the catalysts of the cathode to produce electricity and water.